1. Field of the Invention
The present invention relates to a method of making arrays of micro-optical elements precisely located and having specific optical shapes.
2. Background of the Invention
Micro-optical element arrays are primarily used in the optical communication and optical imaging fields. In general, these applications require that the optical elements have several features. They require control over the shape of the individual elements; the elements must be precisely located relative to each other and other optical components; the optical properties of the elements must be precisely controlled; the elements must be alignable with other optical components; and unwanted optical beams must be blocked and optical cross-talk limited.
There are various method s of making micro-optical elements such as molding, photolithography, and MicroJet printing. However, MicroJet printing is particularly advantageous as to the type of micro-optical elements that can be created and it permits accurate placement of elements within arrays.
Unlike the other methods, the present invention meets all the requirements a precision array demands, it: allows for the creation of specific optical shapes, controls precisely the optical element location, forms an aperture to block unwanted light, allows for the alignment of other optical elements such as optical fibers, and it can use a wide range of optical materials for its manufacture.
This invention provides, for the first time, an inexpensive way of creating micro-optical elements, by utilizing the ink-jet printing method of dispensing optical material for automated, in-situ fabrication of micro-element arrays. The flexibility of this data-driven method also enables variation of the shape of the printed micro-optical element.
The first step in fabricating a micro-optical element by means of inkjet printing comprises providing a substrate. The substrate has a surface with at least one structural opening defined by an edge in the surface leading into a sup port surface. The substrate is preferably an electroform comprising nickel and the structural openings are arranged as an array. The support surface has an aperture through the substrate which is positioned centrally with respect to the edge. The edge is preferably 1 to 5 microns deep so as to define the shape of the micro-optical element. The next step is to provide a digitally-driven printhead containing a hardenable optical fluid suitable for serving as a micro-optical element, preferably an ultraviolet (UV) light-curable epoxy, ejected in response to control signals. Micro-droplets of the optical fluid are deposited into the structural opening of the substrate, preferably centrally over the aperture but if the diameter of the micro-droplets is smaller than the aperture diameter, deposition is preferable over the support surface of the structural opening. In a preferred embodiment, the printhead moves over the surface of the substrate to deposit the optical fluid. The structural opening is then filled until a desired micro-optical element is formed where the element may have a radiused upper or lower surfaces, preferably both. The last step of the process is the hardening of the element, such as by UV light when UV light-curable epoxy is used in a preferred embodiment. Other means for curing such as by heat are also contemplated.
In a preferred embodiment, the production of an array of micro-optical lens elements is described. The first step in fabricating a micro-optical element by means of ink-jet printing comprises providing a substrate. The substrate has a surface with at least one circular structural opening defined by an edge in the surface leading into a support surface. The substrate is preferably an electroform comprising nickel and the structural openings are arranged as an array. The support surface has a circular aperture through the substrate which is positioned centrally with respect to the edge. The edge is preferably 1 to 5 microns deep so as to define and control the shape of the micro-optical element. The next step is to provide a digitally-driven printhead containing a hardenable optical fluid suitable for serving as a micro-optical element, preferably an ultraviolet (UV) light-curable epoxy, ejected in response to control signals. Micro-droplets of the optical fluid are deposited into the structural opening of the substrate. In a preferred embodiment, the printhead moves over the surface of the substrate to deposit the optical fluid. The circular structural opening is then filled until a desired micro-optical element profile is formed where the element may have a radiused upper or lower surface, preferably both. The last step of the process is the hardening of the element.
In another embodiment, the production of an array of elongated micro-optical elements in the form of waveguides is described. The first step in fabricating a micro-optical element by means of ink-jet printing comprises providing a substrate. The substrate has a surface with at least one elongated structural opening defined by an edge in the surface leading into a support surface. The substrate is preferably an electroform comprising nickel and the elongated structural openings are arranged as an array. The support surface has an aperture through the substrate which is positioned centrally with respect to the edge. The edge is preferably 1 to 5 microns deep so as to define the shape of the micro-optical element. The next step is to provide a digitally-driven printhead containing a hardenable optical fluid suitable for serving as a micro-optical element, preferably an ultraviolet (UV) light-curable epoxy, ejected in response to control signals. In a preferred embodiment, the printhead moves over the surface of the substrate to deposit the optical fluid. Micro-droplets of the optical fluid are deposited into the structural opening of the substrate, preferably centrally over the elongated aperture but if the diameter of the micro-droplets is smaller than the aperture diameter, deposition is preferable over the support surface of the structural opening. The elongated structural opening is then filled until a desired micro-optical element is formed where the element may have a radiused upper or lower surfaces, preferably both. The last step of the process is the hardening of the element, such as by UV light when UV light-curable epoxy is used in a preferred embodiment. Other means for curing such as by heat is also contemplated.